Wednesday, May 18, 2011

So, instead of just looking at stuff (which has been the interim state of affairs while I stage puny attempts at migrating my workspace), why don't I actually break something instead? Perhaps veering even farther from my intended path will shake up some progress.

It began, as so many things do, with the innocent notion of exacting a simple task. After having a look at the Alesis units, it occurred to me that a significant portion of the drum machine population here has less than ideal pad response. The idea here was to give a nod to a simple cleaning, and work up from there.

It is my firm belief that opening the case here did not put into motion the sequence of events that spelled doom. Okay, that's a bit over the top, the unit is only on the nuisance list, I didn't smash it with a hammer. Yet.

Another fine example of keeping the analog and logic boards separate, here's the sound production level.

They should have made these in clear enclosures; besides the hand stacking of some caps this thing looks sharp.

So my plan here is to polish the contacts, and wash the conductive rubber buttons with distilled water and coarse paper in hopes that the paper has enough tooth to exfoliate the contact surface of the rubber. As evidenced in the image above, the carbon component of the conductive substrate has leached onto the circuit face, indicating a depletion of conductive particles within the contact patch of the rubber itself, more or less circumventing its ability to act as a switch.

You'll have to forgive me if I'm covering ground that has been trampled to pieces and proven wrong by thousands before me, I'm not a devoted reader of synth DIY lists, and as such am bound to fall into a couple over worn angles.

I digress, the cleaning approach has yet to be proven or disproven, and it looks likely that it will have to wait for either the Alesis, Casio or another Roland unit to be put to test. My intent being not to continue breaking things, naturally.

Incidentally, if you're about to crack the case on your own DR-110 and you wound up here for some encouraging words: watch this power switch button like a hawk. If you're an idiot like me and disassemble it in the living room or other uncontrolled environment, this little blue plastic part may get uppity and travel impressive distances to escape detection.

Imagine this as an animated GIF oscillating between green, blue, yellow and red, and for a moment, before the headache sets in, we can imagine ourselves back in 1999, long before this beast was broken.

So what happened?

Well, I cleaned and polished the bank of switches and put the unit back together. In the past this has always been a battery operated device, but not having a quartet of fresh AA batteries on hand I opted instead to utilize a power supply. I reached for my nice regulated negative tip PSU that I use in lieu of the specified Boss PSA adapter for my PG-300 (so I am pretty fucking sure that polarity is not the issue), plug it in and power it up. Nothing, for a moment, then the distinctive scent of magic smoke.

I don't care how fast you are, even Bruce Lee couldn't unplug something fast enough to avoid damage once the smoke is on parade.

Here's the visible damage (at left) compared to a blow-up of before at right, the trace that was having a go at playing fuse being the likely source of odor. It was still warm after I had grabbed a screw driver and cracked the case.

I notice evidence of someone having been here before, what with the scratching and all. So my immediate suspicion is that something was done here that caused this, and the "fix" wasn't activated until application of DC power years later. This is the safest tack for me to take, as it leaves the most options of actual cause for failure open. I find it generally inadvisable to troubleshoot with too many preconceived notions, as red herring is not my favorite fish.

Beyond taking a picture I haven't done anything with this unit, besides button it back up, plop it in its case and toss it on the to do pile.

Monday, May 16, 2011

Let's have a look at a couple drum machine sections from the organ donor pile.

Here's the drum accompaniment section from the Wurlitzer 4373. This one stands out as being a contender for rehousing due to its compact nature. Pattern selection is achieved via rocker switch as opposed to radio buttons, so stacking up genres does not require a deft hand.

In looking at the neatly stacked PCBs at left, I believe we've got analog sounds at top and digital logic amidst the spread of ICs on the lower PCB. I dig the simple user interface on this thing, visualizing it in a dark wooden enclosure is a snap.

Here are the auto accompaniment modules for a (near as I can figure) 1969 Thomas Organ, each self contained in a stapled shut press-board enclosure.

The "Playmate" was less than forthcoming with offering up a top side gut shot, what with the staples and all, but I'm going to guess that this perspective is actually the more interesting of the two anyway. I believe the circuit board at left contains the sound module portion of things, based on the type of wire connecting. Looks like four primary sounds that are mixed into a drumset (noise and high-mid-low oscillators would be my guess).

The board at right interfaces with the radio button strip, which would probably be ousted for discrete switching in the event I get around to rehousing this unit too. This would be my candidate for pattern source.

They don't make them like that any more, who needs connectors interfacing between the circuits anyway?

And who needs a backing band when they can use one of these? The Band Box. I like this enclosure framework a lot, too bad they wrapped it in cardboard. Potential remains..

My contemplative abilities have sort of abandoned me on this one. I don't see a multi-pattern sequencer and sound source here, so logically I'm leaning toward this being a pattern sequencer. That said, as I recall organs operate via a bank of manually operated switches passing oscillator output, and being that there was not a bank of relays a simple sequencer would meet with difficulty tapping into the oscillator banks (which so far as I know do not respond to CV for instruction). When I was tearing this one down I was in more of an "I need some space" instead of an "I wonder how this works" frame of mind, more's the pity.

A heap of RCA transistors in a (presumably) functional black box. There, I feel better.

Friday, May 13, 2011

Cut some passages in the heap of junk yesterday, more to come. The attempt at a bench in the laundry area hasn't met with the success I had hoped for, so it's back to making this space viable.

Looooong way to go, but being able to access all the corners is a good step.

Floor! It's there. Really. Behind some of that stuff.

I also seemed to have been focusing on a plane either nearer or farther from the subject matter, so blowing those shots up is bound to disappoint. HAH!

Certainly looks the part of the hoarder, but incoming has trickled down to almost nothing. One pending/maybe sort of acquisition, then it will only be the truly rare finds of the sort that find me to add into the pile.

Tuesday, May 10, 2011

Took part in an organ grinding party last weekend.

Wurlitzer 4373, the organ donor.

Not really a whole lot to it, the disassembly that is. Most (if not all) console organs were built by hand, which is a boon to disassembly as it can be achieved with simple hand tools and minimal destruction. Pictured above are some sections of the Orbit synthesizer that was being extracted prior to tossing the rest into a rendering pot.

I picked up most of the remaining mash, including woodwork which was promptly flattened into as close an approximation of sheet stock as I could muster with minimal fuss. Included in this heap of discrete transistor constructions was the above contained circuit, sealed away from curious fingers. The ICs are marked "X", Google isn't being very helpful regarding coughing up a datasheet. I'm guessing it's a high frequency circuit based on tuning cap and that weave of wire, which probably exhibits just enough capacitance for that shape to be meaningful.

I love looking at this. I'd hate to have to work on it (more than I have to, what with some of these old mixers hanging about) so it's a lot easier to plunder guilt free.

Monday, May 09, 2011

A little internet investigation indicates a likelihood that this is due to a failed back-up battery, a Tadiran TL5101. This was built early 1990, so it is reasonable to assume the battery is toast.

The above sentiment applies to the entire family here. I'm going to crack the case on each of these to confirm that the TL5101 package is the same on all, as I really hate having to improvise with batteries when an easier option exists. For what it's worth, there are three available packages of TL5101, and a variety of PCB revisions for the Alesis units.

While I have the trio together it makes sense to do a quick run through of each and earmark attention areas I should address while the case is cracked and I'm changing the battery.

The MMT-8 was a bad amp room unit, so my expectations were low. Powers right up, logic responds without readily apparent glitches and the pad response is very crisp. This must have been in the boneyard due to a misplaced wall wart.

The HR-16 was purchased used in 1998. The pads are in complete need of rework, this unit is almost unusable as is.

The HR-16B was a trade a year or two ago, pads require a firm hand but respond under pressure and the volume and data sliders had been sheared. It also needs a back-up battery.

The axial 1/2AA package is standard across all three examples in my possession. Inorganic.

I had envisioned some level of nuisance in regards to the sliders (mind you, I have not yet narrowed them down to a part number and learned of availability).

Any concern I had regarding remove and replace is unfounded however.

Concern over the Alesis QC is another story, though in their defense this unit has run for over two decades (it could buy beer if it was so inclined) so the unseated IC isn't detrimental, it does however stick out like a sore thumb.

Conductive rubber keypads are, in my opinion, a tool for post warranty failures. Perhaps I have never happened upon the right mix of chemicals to replenish the conductive nature, and I've always been wary about trying a conductive paint for fear of adhesion failure making a huge mess. So it looks like aluminium foil to me. I'll do a bit more research before actually performing this irreversible modification, but if my other option is trying to punch through the PCB traces I'll clad these nipples in foil at the drop of a hat.

Keypad modification sounds a lot more pleasant than fabbing another interface PCB.

Here's where the velocity information comes from, a quartet of piezo discs on the backside of the drum-pad section.

Motherboard time:

MMT-8

HR-16, looks like a Rev. A in referencing the service documents.

HR-16B, service docs indicate this is a Rev. AQ, so I'm going to climb out on a branch and speculate that the revision sticker at lower right refers to software, not hardware.

Wednesday, May 04, 2011

Looking at yesterday's thumbnail format stretch artifacts is like bludgeoning my tired eyes with a dirty sock full of semi-liquid smelly cheese, so I'm going to push the envelope on my quality vs quantity check valve in an attempt to make those blurry images fall off the front page.

Brute force once again takes first chair at the opportunity to fine tune, forgive me, juggling computer code does not represent the satisfaction of hitting my thumb with a hammer.

About two years ago I spied an old tube radio on craigslist for a price I couldn't pass up. It's an old push-pull 813 that has seen better days. Having no intent to invest a large chunk of time to jump through the FCC hoops required to operate on the AM bands, and given the condition of the unit at the moment I'm thinking more along the lines of repurposing the enclosure, and reusing the salvageable parts.

Rats nest wiring.

Dusty 813s and tuning capacitors.

I remain fascinated with the notion of having a go at cloning a Fairchild compressor (well, two, for stereo) and keep being reminded of that fact when I look at this thing.

Tuesday, May 03, 2011

Played a set last night, this seems like as good a time as any to dip into the original intent of these pages, talking about gear (from the on the surface standpoint). I'll also break my established landscape image orientation habit. (well, it appears the stretch involved in retaining my format width makes the nested portrait image look much more low resolution than it actually is, probably won't be doing that again.)

Here's where the rubber meets the road. There are several feedback loops going on here, some of which are nested in a count the triangles sort of way.

Pulse feeds EQ.EQ splits output into three feeds, to a line mixer channel and "Aux in" on each 6300.Each side of the 3630 is fed from "Link B" total summed output from one 6300, the signal is returned to the "Link B" input which bears no manual level control (amplitude being controlled at the 3630)PA output of the 6300 has a level control, each 6300 feeds one side of the stereo fuzz, which in turn feeds two line mixer channels.6300 Link A output feeds SMX-880 directlyEach side SMX-880 XLR output feeds channel 1 of the corresponding 6300.XLR "transmit" output of each 6300 feeds channel 2 of the other.The image above also shows the 1/4" output of the SMX-880 feeding its own 7/8 channels, but those were spare cables, unplugged to allow connection to the PA system.

Having but a single rolling rack as a live set-up is enjoyable compared to the heap of shit I used to carry, but the low frequency department is not highly represented which is something of a problem in the long run..

Monday, May 02, 2011

Perhaps I should change the running title to "broken stuff" instead of "machine log", especially since most of what I focus on isn't technically machinery in the first place. Nah.

Here's a GenRad 1390a noise generator.

The power switch was already sheared when I bought it, and being a three position rotary wafer it will not be as simple as slapping a SPST in there.

Gutshot.

Here's the heart of the noise generator, a 6D4 in a magnetic field, sort of the tube era equivalent of a lifted collector. Okay, not really a firm parallel there, but work with me here.

I think this unit saw some service, as there are a few thermal stains on the chassis. I'm pretty sure the shake and bake coating on this cap has more to do with a "sticky" shell picking up airborne debris than heat, but the airborne material was probably agitated by the heat and magnetic charge of the powered device to begin with.

More selenium, which reminds me I have a backlog of simple surgeries to perform with no excuse..

Sunday, May 01, 2011

Mayday! Time to get some progress and self serving industriousness laid out, and resume paving the path to the future.

Forging a bit of progress on the CNC project. Smoothing out nicks and surface irregularities of the structural material through a gentle file hone and fitting the bearings onto the screws as outlined following.

In preparation I stuck the screws in the freezer for the afternoon, and the bearings in an oven (initially at 250 f) for ten minutes. I forget the actual room temperature dimensions, as they were compared at ODD a while back, but it did amount to an interference fit. The hope here was that between thermal expansion and contraction a fit could be made without the necessity of an actual press.

Note the frosty condensation at left offset by the heated metal at right, the metal cylinder was the bearing race "anvil" to alleviate hammer shock from being transmitted through the bearing itself. The first two involved hammering at the coupling end. This wasn't a huge concern as the coupling end is not a super critical precision surface as it will be floating to allow drift from minor misalignments to be taken up at the coupler as opposed to premature wear on the bearing surfaces (no mushrooming occurred).

The second bearing was a bit more resistant to installation, probably due to the cooling of the bearings during the first installation; so the third bearing was heated at 350 for five additional minutes. Additional heat was the key, as the third bearing required no hammering at all.

Installed, ready to move on to structural plotting, based on actual measurements of installed screws.